


Viscosity

by sylvermyth



Category: Voltron: Legendary Defender
Genre: Angst, Hurt/Comfort, M/M, Mutual Masturbation, Other, Shadam, Sheith endgame, Venom AU, breaking up, venom!keith
Language: English
Status: In-Progress
Published: 2018-11-05
Updated: 2018-11-05
Packaged: 2019-08-16 19:57:58
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 6,469
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/16501766
Author URL: https://archiveofourown.org/users/sylvermyth/pseuds/sylvermyth
Summary: The thing about the Garrison is, they’re always hiding something.  Or at least only telling half-truths.Shiro dreams, while he’s under.  It starts as a blackness, a void, but red and violet suffuse the darkness, slow and uncertain.  Curious, almost, until the void coalesces into something solid, black on black so that Shiro can’t see it so much as sense the shape.  Alien, his mind cried, even before the thing blinked narrow yellow eyes at him.  Shiro’s jaw tightens, his dream-self already settling into a defensive posture, fear singing through his nerves, but the dream spectre only stares with its unnerving yellow eyes.





	Viscosity

**Author's Note:**

  * For [Shklance_Beef_Sandwich](https://archiveofourown.org/users/Shklance_Beef_Sandwich/gifts).



> This fic is my (late) Halloween sheith exchange fic for [@shklancebeefsandwich](http://shklancebeefsandwich.tumblr.com)! They weren't particular about what they wanted to read, but I noticed a lot of Venom reblogs and was...inspired... XD Disclaimer because I haven't had a chance to actually see Venom myself yet, but this is an AU so...creative license? Anyway, I'm sorry this is a WIP right now, I hit like 4k and realized there was no way I could complete this as a oneshot within a reasonable amount of time; I hope you at least enjoy what's here and what's to come!
> 
> Thank you as always to my wonderful beta, [caseyvalhalla](http://caseyvalhalla.tumblr.com) who is always there to help me brainstorm and make my words pretty and my smut scenes BETTER. ILU BAE!!
> 
> (Also there is monsterfucking in this, you're welcome.)

It’s supposed to be an alternative to the stimulants he required to keep his body in peak shape--which, honestly, he doesn’t mind _now_ , but his condition would only get worse with age.  Shiro might not have even considered it if not for Adam’s insistence, but it could prolong Shiro’s career as a pilot, and with the Kerberos mission on the horizon... Shiro decides to give the _treatment_ a chance.  The risks are minimal, the doctors assure him, and he has no reason to doubt them. After all, Shiro has every faith in the Garrison.  Even the sterile laboratory atmosphere is evidence of the Garrison’s dedication to moving technology ever forward.  Right?

Shiro shoves down his apprehension and lets them take his clothes in exchange for a hospital gown, lets them wheel him down another hallway to another sterile room after a kiss and reassurance from Adam.

The thing about the Garrison is, they’re always hiding something.  Or at least only telling half-truths.

Shiro dreams, while he’s under.  It starts as a blackness, a void, but red and violet suffuse the darkness, slow and uncertain.  Curious, almost, until the void coalesces into something solid, black on black so that Shiro can’t see it so much as _sense_ the shape.   _Alien,_ his mind cried, even before the thing blinked narrow yellow eyes at him.  Shiro’s jaw tightens, his dream-self already settling into a defensive posture, fear singing through his nerves, but the dream spectre only stares with its unnerving yellow eyes.

He won’t process the mouthful of sharp teeth that define its mouth until later, after the dream is over.

.o.

“Shiro.”

It’s not Adam’s warm voice that wakes him, but one that grates in his head, hoarse and cracking, breaking over the two syllables of his name.    There’s a foreboding sensation of someone considering him, but when Shiro manages to pry an eye open, there’s no doctor or nurse peering at him over a clipboard. Only Adam dozing on the chair in the corner of the room, his glasses askew on the bridge of his nose.  Shiro blinks away the lingering grit in his eyes and shifts on the hospital bed, searching for the owner of the voice.  The movement is enough to wake Adam, who greets him with a tired smile, but instead of feeling comforted by it, Shiro’s anxiety spikes and the machine monitoring his vitals screeches.  It’s annoying, and Shiro paws at the devices attached to him.

“Takashi?”  Adam’s smile slips, but Shiro only sees it in periphery.  “Hey, babe, calm down. It’s alright.”  He closes a hand around Shiro’s wrist, “Breathe, Shiro,” and Shiro lets his voice soothe him, though he still feels...off.

“Sorry,” Shiro croaks. He tries to wet his lips but his mouth is bone dry; Adam looks  concerned and releases Shiro’s wrist to pass him a cup of water. There’s a swell of gratitude in his chest as he gulps it down, but the anxiety isn’t abating.  He frowns, mouth hovering over the lip.  “I guess I’m just. A bit disoriented.”

Adam straightens. “Do you want me to call for the doctor?”

Shiro’s vision goes red, and the voice that comes out is his, but the words are disjointed, like someone else is using his mouth, a low, “No, I’m fine.”  There’s a hint of an edge to it, and Adam gives him a considering look.

”That’s good.”  Adam purses his lips and adjusts his glasses. “Still, I’m going to go let the nurse know you’re awake.”  He squeezes Shiro’s hand with familiar affection on his way out, and it’s something that Shiro should be happy about—that he’s got someone here waiting for him after the procedure—but that agitation simmers just below his skin.  Shiro watches Adam’s retreating form and then—

“ _Now!”_

It’s the voice that he woke to, though there’s no one else in the room.  Shiro jerks his head around to confirm it—or at least tries to. His body isn’t cooperating with him.  He briefly wonders if the procedure had done the opposite of what was intended, if it had accelerated his degeneration, but that can’t be it because his body _is_ moving.  Just, on its own.

“ _Have to go.  Not safe.”_

Shiro’s a passenger in his own body as his hands rip away the sensors and the IV, the machines beeping in protest, but Shiro’s too distracted by the black... _ooze—_ there’s really no other word for it—that erupts from his skin and covers it. It’s alarming, the oily black enveloping him from head to toe, slick and surprisingly warm, and oddly...protective?  He doesn’t have time to dwell on it because he’s moving still, a shadow creeping out the door and tight against the wall, fast enough to escape the notice of Adam and the nurse he’s talking to.  There’s a group of scientists crowded around a workstation, their backs turned, and Shiro pauses, feeling a flicker of anger towards them that’s not his own, before he’s moving on again.

 _Shiro.  Where is it safe?_  By now Shiro realizes that the voice isn’t audible, that it’s directly in his mind, but it’s not _him_ ; it’s separate, other.   _Other, yes.  Separate, no._  The response is annoyed and a little distracted.  Distracted by maneuvering him, Shiro realizes.  _Us.  You and me_ , the voice in his head says.   _Also I’m not The Voice.  I’m Keith._  The annoyance is even clearer now, and the black sheathing Shiro’s skin constricts a little.  It’s not uncomfortable, but it feels like an admonishment.

“Okay, uh, Keith,” Shiro says--and at least he has control of his own voice--”nice to meet you?  I guess?  I’m Shiro.  What’s--what’s happening?”  He wants to ask more, has a thousand questions clamoring up into his throat until he’s almost choking on them, on the verge of panic because _what the fuck is going on?_ \--but he takes a deep, steadying breath.

It’s definitely strange, being passive, being able to take that steadying breath, when his body is being controlled by something else. Shiro doesn’t dwell on it, and instead focuses on calming himself, approaching this as rationally as possible, considering, because panic never helped anything.  By the time Shiro is slipping outside, he’s managed to prioritize his questions, starting with, “How are you controlling me?  And where are we going?”

There’s something approximating an exasperated sigh in his head.   _I **am**_ _you.  We are going to find safety, away from **them**_.  Shiro doesn’t find the response clarifying at all, until a flurry of images tumble into his head:  the black shape from his dream with its narrow yellow eyes; a viscous fluid in a tank that seethes against the glass walls until it’s allowed a _host_ (the word is Keith’s, he realizes), but the host isn’t right when it settles in, they’re weak and dying and unreceptive—black oozes out of the host’s skin to escape death but it’s a near thing.  The process is repeated again and again, Keith forced to cling to life under the scrutiny of people in white lab coats and he’s scared and he wants to fight but first he needs to find _a host_ —and then they bring him Shiro.

“Parasite,” is the word that comes to mind, but there’s a visceral recoil before Shiro can even say it aloud.   _No!_  Keith offers no other explanation, and the agitation that has been buzzing under Shiro’s skin is gone, like a door slamming shut. It makes the whole not-in-control situation even more unnerving, especially when Shiro finds himself vaulting up over a fence that should be too high, too dangerous with the razor-sharp barbed wire topping it.  But there’s no sting, no shock as he drops to his feet on the other side.  It surprises him, but everything has been a little bit crazy since he woke up and the surprises are piling up enough that this seems minor in comparison.

 _Not a parasite,_ Keith says after they’ve been running for a few minutes.  It’s quiet in his head, a little hurt, and Shiro doesn’t know what to make of it.  He still doesn’t understand everything, but he’s never been a person to hurt others, and there’s a little remorse for maybe hurting Keith, whatever Keith is.  Especially since Keith has offered him no harm—he takes quick stock of himself as best as he can, but he’s uninjured.  It’s just... Weird.

Shiro’s figured out where they’re going by now, or at least, he thinks he has, because it’s the same route he would take to go home to his and Adam’s apartment, though they’re still sticking to the shadows, out of sight.   _Home is safe_ , Keith offers, and Shiro can’t help but agree.  Shiro had felt safe enough at the Garrison hospital, but the trickle of memories from Keith is making him re-evaluate the safety of the facility.  He’s still unsure about Keith, but if Shiro is to believe the images in his mind, the Garrison is at the very least not what he thought it was--and they’d lied to Shiro, if Keith is the result of Shiro’s ‘procedure.’

Shiro’s still trying to process everything when they reach his building.  He doesn’t have his keys, but he watches as the black ooze extends from his arm and slips through the gap under the door until it’s opening.  He’d half expected to break through it, and there’s a flicker of that annoyance from Keith again.

_You would not like it if we broke through._

“No,” Shiro agrees, bemused.

He’s relieved when they finally come to a stop in his apartment.  They’re standing in the center of the living room, tense and uneasy, but finally still.

_This is safe?_

“Uh.  Yes?”

The black ooze covering him recedes back into his skin, and Shiro can’t stop staring at where it disappears on his forearm.  He’s back in control of his own body, too, he realizes, and as soon as the thought occurs, his knees try to buckle at the weight of _everything_.  There’s a scoff as his body catches itself--as _Keith_ catches him, and guides him to sit on the sofa.

Once he’s there, he feels his skin prick across his chest, until an amorphous black _thing_ sprouts there, coalescing into--a face?  Or something approximating one, with yellow eyes and dagger-sharp teeth that would put a shark to shame, long pink tongue lolling out grotesquely.  Any calm that Shiro’s harbored up until now evaporates, a bolt of fear coursing through him, fight or flight instincts screaming, but it’s _attached_ to him, and there’s no running away from that.

The yellow eyes blink at him, slow and deliberate, and the face shifts and changes, the teeth shrinking and disappearing behind human lips, the black lightening into something softer, more approximate to skin than sludge, though there’s still a violet hue to it.  The face is still crowned with black, but it looks more like hair now, and the thing expands until it’s more than just a _disembodied head_ ; now there’s a broad set of shoulders and crossed arms and Shiro’s not sure if it’s better or worse, considering it seems to be coming out of his own body.

“Better?” it says, and it’s Keith, Shiro realizes.  “What were you expecting?”His teeth are still sharp behind his lips, visible as he speaks deliberately.

“I don’t know.”  If there’s an edge of hysteria in his voice, Shiro thinks it’s warranted.  “Can you tell me what’s going on?  What _are_ you?”

“ _Not_ a parasite.”  Keith lifts his chin.  “Parasites are…” Keith purses his lips, as considering his words.  “Harmful.  I think the word is symbiote.  Yes. Symbiote. That is what I am.”  He tilts his head.  “You were unwell.  They only gave me sick hosts, but you were the first one I could help.”

“Wait. Wait-wait-wait.  Ok so. You’re inside me?”

Keith gives him a significant look and then tilts his head to draw Shiro’s gaze to the tendril of black that is unmistakably coming from his own chest.  “I thought that was already clear,” he deadpans.

Shiro runs a hand over the short hair of his undercut, chagrined.  “It’s different to say it out loud.”  Keith gives a noncommittal hum.  “Ok.  Alright.”  Shiro’s questions are clamoring for answers again, and he tries to focus on a single one, but it’s _hard_.

Before he can vocalize another one, though, Keith huffs a sigh and Shiro’s flooded with thoughts and memories that aren’t his.  They’re surprisingly ordered, and the first thing he knows is that Keith is giving these to him, to answer his questions and help him understand.

Keith isn’t from Earth.  It’s not a surprise, but Shiro is startled by the memory of hurtling through space, faster than anything the Garrison has ever developed, stars blurring into lines from the speed of it, impressions of star maps with constellations that he’s never seen before.  There’s urgency in the voyage, fear driving him to find safety because he’s been compromised, and Krolia-- _family_ \--had found refuge on Earth, once.

Keith isn’t so lucky.

His stolen ship malfunctions in Earth’s atmosphere, and the resulting crash landing leaves him vulnerable.  Shiro recognizes the Garrison vehicles that converge on the wreckage, Haz-Mat suits looming with heavy cylinders that Keith is too weak to escape.

Keith only gives Shiro a vague impression of the tests the Garrison run on him, a reminder of what he showed him in the hospital.  Instead, this time Keith focuses on showing him the damage in Shiro’s cells, the disease that would slowly take his life--except that Keith is part of Shiro now, all the way to the cellular level, and with little effort Keith _fixes_ him.   _Not a parasite_.

And this, Shiro realizes, was the so-called _treatment_ the Garrison had offered him.

Shiro’s healthier than the other hosts that Keith’s been given, not so far gone that he’s beyond repair, but more importantly, he’s good and right and a _match_ , and Keith immediately loves him.  He stays quiet under Shiro’s skin, biding his time until there’s less attention on them so they can _escape_.

Shiro’s idealistic, sure, but he’s not naive, so the Garrison’s actions aren’t as much of a shock as they could be.  That doesn’t stop the sting of betrayal, though, when he’s given so much of himself to the Garrison.

Shiro leans forward to drop his head in his hands; Keith anticipates the move and shifts to the side.  “They’re not done with us.”

“No,” Keith agrees.

Shiro draws a deep, steadying breath.  “They know where I live.  It’s not safe here.  Unless…”  Shiro straightens and catches Keith’s gaze.  “They don’t know everything about you.  It’s why they’re studying you, right?  So far all of their experiments”--Shiro feels his flare of anger echoed in Keith just at the thought of it--”have ended in rejection.  So they don’t know what happens if you’re _not_ rejected.  For all they know, you dissipate into my system and that’s that.”

Keith’s form flickers minutely, reverting to the black, viscous thing Shiro had first seen, before settling back into his humanoid shape, his expression shuttered.  “You don’t want to expel me.”

Shiro blinks.  “What?  No.  I mean, this is all very, very strange, but you can’t survive for long without a host, right?”  At least, that was the impression Shiro had gotten; Keith confirms it with a nod.  “And if I can convince the Garrison that everything is normal, they won’t have anything to pursue.  They don’t know you’re...you.  That you can communicate with me.  They don’t know I found out about their _procedure_.”

Shiro can sense Keith sifting through his thoughts, and it should feel like an invasion of privacy, but he’s not hiding anything.  “Okay,” Keith says reluctantly.  “We can try.”

Shiro’s on the verge of saying _It’ll work_ when there’s a noise from outside the apartment, feet pounding in the corridor, and Adam’s breathless voice.

"Shiro?”  Adam’s voice is muffled by the door, and Shiro hears him curse as he drops his keys.  “Shiro, are you here?”

Before Shiro can even react, Keith’s form is collapsing into puddles of black that seep under his skin, and it’s a strange sensation, because Keith is gone but he’s _still there_ , settling somewhere within Shiro.

“Takashi!  Thank god, you’re here.”  Adam rushes into the room and collapses on his knees in front of Shiro, taking a deep, shuddering breath.  “Are you okay?  I went back to your room and you were gone--nobody even saw you leave!  And look, you’re still in that damn hospital gown, and no shoes.”  He’s upset, and Shiro can’t blame him.

Shiro lets Adam take his hands and squeeze them between his own.  “Sorry.  I--I was disoriented when I came to.  I guess it was easier to just come home, or some kind of instinct, because I barely remember how I got here.  I’m okay, though.”  It’s not a lie, but Shiro knows he is going to have to hide Keith’s existence even from Adam, and the thought of it hurts.

 _You trust him,_ Keith murmurs, _but not with this?_

Shiro doesn’t know how to explain to Keith that it’s more complicated than that, that Adam might not be as receptive to Shiro harboring an alien symbiote as Shiro is himself.  He doesn’t know, and he’s not willing to risk it.

Adam frowns at him.  “I was worried, you know.  The nurses and the doctors were upset--understandably.”  Adam shifts his grip on Shiro’s hands to retrieve his phone from his pocket, only glancing away long enough to unlock it.  “I’m going to call them to let them know you’re ok.  They still have to check you over, make sure everything’s ok after the procedure.”

There’s a flicker of unease from Keith, one that Shiro shares, but Shiro tamps down on it; they have to cooperate to avoid suspicion.  “Yeah, of course.”  Shiro reaches out and smooths the crease between Adam’s brows as he dials the Garrison hospital.  “Sorry, baby, I didn’t mean to worry you.  Thanks for being there when I woke up.”  And Shiro means every word, because Adam has been there for him through so much, despite the obvious strain it puts on him.

Adam’s face softens and he squeezes Shiro’s hand.  “Of course.”  Shiro can feel Keith at the back of his mind, curious about this interaction, but remaining silent, even as Adam straightens  to press a kiss to Shiro’s temple.  Adam settles next to Shiro on the sofa, still holding his hand, as he tells the Garrison staff on the phone that he’s found Shiro and that he seems well.”

“I’m sick of hospitals,” Shiro announces when Adam ends the call.  It’s on the nose even if it’s an excuse to avoid whatever the Garrison still has in store for him and Keith.  It’s only delaying the inevitable, but Shiro wants to buy a little extra time to figure out a game plan with Keith.  “Can we stay here a little longer before we go back?”  He leans into Adam, trying to garner some sympathy, and he knows he’s succeeded when Adam leans back, bringing a hand up to stroke Shiro’s hair.

“I know, babe.”  Adam heaves a sigh.  “We can stay a little longer.”

.o.

If the Garrison hospital staff suspect anything about Shiro and his new symbiote, they don’t let on.  They insist on a full gamut of tests, under the guise of monitoring his reaction to the procedure, which is to be expected, but ultimately they only tell him his response is promising, and that they’d like to run more tests.

Shiro and Keith endure it, Keith quiet under his skin whenever there are eyes on them—at Shiro’s insistence. He can tell Keith doesn’t like it, and they steal moments when Keith can emerge into open air, black spilling over Shiro’s skin and sometimes that’s enough, and sometimes Keith settles into something more substantial, takes a humanoid shape.  Occasionally, he blankets Shiro from head to toe, like he did when they ran from the hospital, and Shiro can feel the potential in the form, and wonders what to do with it.  Maybe, when the Garrison decides there’s nothing more to learn, they can find out.

_We could eat them and be done with it._

Shiro’s in the middle of a Garrison corridor when Keith says it, and the suggestion makes him stumble.  He glances around, but it’s between classes and the corridors are teeming with students and staff alike.  He manages to keep his mouth shut long enough to duck into a closet, hissing under his breath as soon as the door is shut.  “ _Eat them!?_ ”

Inky black snakes through Shiro’s uniform until there’s a miniature Keith face glaring at Shiro through the low light of the closet.  “Yeah, why not?  We’re strong enough now.”

Shiro sputters.  “We can’t just _eat_ people, Keith!  It’s...that’s murder, it’s wrong.”

Keith balloons up, yellow eyes narrowing as he stares Shiro down.  “What they did to us is wrong.”

“That’s true, but that doesn’t mean we can _eat_ them.  And that’s not a solution, Keith.”  Shiro rubs the bridge of his nose.  “The people who did this to us were only working under orders.  And even if they weren’t, dead Garrison staff would draw too much attention.”

“You don’t want them dead?”  Shiro can feel Keith’s surprise at the knowledge, and the disappointment.  He thinks he should be more shocked that that’s Keith’s reaction, that maybe he should condemn Keith for it, but he can’t bring himself to.

“No,” Shiro murmurs, “I don’t want anyone dead.”

“But I’m hungry, Shiro.”  Keith’s expression morphs into something close to a pout.  “We don’t eat enough.”

Shiro crosses his arms and narrows his eyes at Keith.  “First of all, that does not mean _go eat people_.  Eating people is strictly not allowed.  Second of all, if you were hungry, why didn’t you say so?”  Keith ducks in what Shiro supposes is an approximation of self-consciousness, but doesn’t answer.  “Okay...we’ll talk about this more later.  For now we have a class to teach.”  Keith gives him one more pointed look before receding back under his skin, and Shiro can tell he’s sulking in the back of his mind.

It’s distracting, especially as Shiro himself can’t get past the fact that Keith would consider _eating people_ , and if he’s not quite as focused on teaching as he should be, he supposes he can’t be blamed.  He resolves to make sure Keith’s appetite is satisfied on something other than people, and that includes showing Keith that there are better things to eat.  Like Mac and cheese.

It turns out that Keith’s tastes don’t quite line up with Shiro’s own.

_Mac and cheese is gross._

They’re in Adam and Shiro’s apartment alone, a spread of takeout food on the table that should be enough to feed a whole family, and Shiro’s not sure if he’ll be able to explain to Adam why he ordered so much food in the first place.  He needn’t have worried, though, because Keith reaches out in puddles of black and when the black recedes most of the food is gone.  The Mac and cheese is untouched, and Shiro snatches it up, mildly offended (but secretly pleased).  “Mac and cheese is the best, is what you meant to say.”

Keith solidifies into a face, and he pointedly rolls his eyes. “Nope. Gross, yuck.  Hate it.”

“Whatever, that just means more for me.”  Shiro sticks his tongue out, and Keith responds in kind—except Keith’s tongue lolls out much farther than Shiro’s.  It’s oddly endearing, though Shiro thinks it should probably be gross.  He stabs a fork in his Mac and cheese and eats it with relish while Keith gives him judgemental looks.

Shiro raids the leftover Halloween candy for dessert, and that’s how they discover Keith’s love for chocolate, black sludge rippling with joy as he snaps up Hershey bars as quickly as Shiro unwraps them.

Shiro’s getting used to being _we_ instead of _me_.  He’s getting used to Keith’s demands for food--he _always_ wants chocolate now--and Shiro’s grateful that he has enough disposable income that it’s not a burden.

Adam is another issue entirely.  He’s been at Shiro’s side long enough to be familiar with the hospital visits, and it’s never been easy.  Despite the Garrison promising a treatment to Shiro’s illness, the ensuing tests have him in the hospital more frequently than before, even though his disease appears to be gone ( _is_ gone, Keith assures him).  It puts a strain on Adam, and as a consequence, their relationship, especially with both of them still fully engaged in their roles at the Garrison.

And that’s only the surface of it.

It’s not easy to keep something from a person he cares for so deeply.  Shiro doesn’t like doing it, either, but intuition urges him to keep Keith’s presence to himself.  Keeping such a big secret takes its toll, especially when Keith is constantly in his mind and has invariably become a part of Shiro.  There’s so much he can’t talk to Adam about now--Keith’s sullen silences, his chocolate cravings, his bouts of sharp humor.  The joy that bubbles up when they fly in the simulator--the Garrison hasn’t cleared Shiro for flight yet, but with Keith’s help his reactions are sharper, quicker.

_Can we eat Iverson?_

Keith had woken Shiro up in the middle of the night to sneak out into the desert on his hoverbike.  They’d managed to slip out of bed without waking Adam up, but Iverson had caught them riding back in just before dawn and chastised Shiro for it.  It was a light admonishment, a brief lecture on Shiro’s status as a role model for the underclassmen, but it was enough to make Keith bubble irritably under his skin.

Still, there’s a hint of teasing in Keith’s tone, and no real intent in the words.  “That’s not funny, Keith.”

Keith is still lurking out of sight, but Shiro can practically feel the smirk directed at him.   _You think it’s funny._

“A little bit,” Shiro admits, a smile tugging at his lips.  “The cadets wouldn’t complain.”

Shiro’s smile dies when he climbs back into bed with Adam.  He wants to wake Adam and tell him about this adventure, about Keith joking about eating people because it’s morbid but totally _Keith_ , except...he can’t.  He’s pretty sure it wouldn’t go over well at all, even though it would explain everything he’s done wrong since his _treatment_.

Shiro knows where this is going.  He knows a relationship isn’t sustainable like this, but he still tries.  Adam would probably forgive him, would help Shiro make it work, but the intimacy between them is rapidly eroding.

Shiro had begged off Adam’s attentions the first few days after the _procedure_ , hiding behind it as an excuse, but he can only rely on that for so long.

A week later, Shiro breaks away from a heated kiss, claiming exhaustion from Garrison duties.  The look on Adam’s face almost breaks him, but Adam gives him space.  It’s not that Shiro doesn’t want him, doesn’t want to go where they were going, quite the opposite--it’s that Shiro can feel Keith in the back of his mind, curious and attentive.

 _Were you going to eat Adam?_  The question startles Shiro while he’s brushing his teeth, and he nearly chokes on the toothpaste in his mouth.

Shiro manages to spit and drag in a breath before he hisses, “What?  What the fuck, Keith?”

 _You felt hungry._  There’s a mental shrug.   _I can help with that._  Keith manifests his face with its wicked sharp teeth and snaps his jaws to emphasize his point. _If you like him too much to eat him we can go find someone else.  You told me not to ignore hunger, Shiro._

Shiro puts his toothbrush away and rubs his temples.  “It’s--it’s not that kind of hunger, Keith.”

Keith gives him a blank look, and Shiro realizes Keith has no idea what he’s talking about.

“I’ll tell you about it later,” Shiro mutters, because Adam is waiting for him in the next room and he’s really too tired and frustrated to try to explain it.

Shiro hasn’t figured out if there’s a way to block Keith out (and he’s not sure he wants to).  But it’s awkward to consider sex with Adam when Keith is riding shotgun.  He’s not sure how Keith would react, and worse...Shiro’s uncomfortable with the fact that Adam doesn’t know there’s a third party involved.  It’s a breach of trust worse even than keeping Keith’s existence a secret, in his opinion.  He curls up next to Adam, and the distance that’s growing between them is almost palpable.

Shiro starts wondering when he’ll be cleared for flight, if it’ll be in time to secure his position on the Kerberos mission, and it’s one of the few things he can still voice aloud to Adam.

It’s a mistake.  Shiro sees it in the expression behind Adam’s glasses, in the tightening of his mouth, but Adam doesn’t say anything.  It means he wants to think about his response, because he needs to temper his reaction.  “Give it time,” is what he says, finally, but Shiro knows he wants to say more.  It hurts, a little, and Shiro can feel Keith growing angry at the back of his mind, and also confused.

 _There’s no physical damage,_ Keith says, _but he hurt you.  Shiro, I will eat him for you. He hurt you._

“No,” Shiro murmurs.  “No, Keith.”  He wants to say more, to remind Keith that they don’t eat people, but he’s tired and heartsore.

Shiro does get cleared for flight not long after, though there’s still some uncertainty where the Kerberos mission is concerned.  Shiro wants it, more than anything.  Not because he needs to set more records, or simply add another notch to his belt--he just loves being in space.  It’s where he’s meant to be, surrounded by constellations and an incomprehensible vastness that can’t be captured by any simulation, can’t be grasped from the Earth’s surface.

Shiro wakes up a week before the final decision is supposed to be made.  It’s a Sunday, late morning light slanting through the blinds, striping Adam’s skin with it until he rolls over, blinking sleep from blurry eyes.  He’s not wearing his glasses, and that paired with his mussed hair makes him look soft and beautiful, and Shiro loves him, he does, but there’s guilt clawing at his heart, because he realizes he’s already starting to let go.  The cracks in the foundation of their relationship have been growing, and it’s become a canyon after all the strain.  Shiro reaches out to brush Adam’s hair away from his face, and this is where he should close the distance between them, should show Adam how deep his affection runs, but he doesn’t.  Shiro doesn’t think it would be fair, anyway, so he only presses a soft kiss to Adam’s lips before climbing out of bed.

Keith is uncharacteristically quiet in the back of his mind.

The decision to allow Shiro to pilot the Kerberos mission is a controversial one.  There’s no traces of his disease, but there’s an anomaly in his cells that the Garrison lab staff can’t explain--it’s Keith, Shiro knows, but he’s not about to give them that information.  The higher-ups are uneasy sending him back into space, but Sam Holt is leading the expedition and doesn’t want another pilot; ultimately that tips the decision in Shiro’s favor.

It’s not a win without consequence, and even though Shiro’s braced for Adam’s reaction, it still hurts when he says, “Don’t expect me to be here when you get back.”

Shiro’s grateful that the preparations for Kerberos keeps him too busy to dwell on it.  For the most part, anyway--he still has to pack away his things and put them into storage.  Keith helps in silence, wrapping around Shiro and lending him strength to carry boxes when there’s no one around to see.  Shiro takes comfort in it, and though it’s hard to adjust to sleeping alone again, he’s still got Keith for company at the back of his head.

_Is it because you couldn’t eat him?_

“What?”

Keith manifests as a face, because he knows Shiro likes to look at him if he can.  “You were always hungry around Adam.  Is that why you are unhappy, because you couldn’t eat him?”

Shiro settles an affectionate hand on Keith’s miniscule head.  “No,” he says tiredly.  “I told you, it’s not that kind of hunger.  It’s like…”  Shiro doesn’t want to talk about it, really, not now, but he wants Keith to understand this.  “It’s an instinct like hunger, but it’s different.  Makes you want to feel good, want to feel good with your partner.  I wanted to--I used to, with Adam, but…”  Shiro trails off.  “It goes deeper than that, though.  I loved him.”  Still love him, Shiro thinks, because it’s going to take time to get past this.

Keith blinks up at him, contemplating, and says, “An emotional attachment.”

“Yeah,” Shiro says, his voice cracking around the word.

“Emotional attachments are taboo among my kind.  If it hurts like this, I can see why.”  Keith tilts his head.  “Why form attachments to begin with if this is the result?”

Shiro shrugs.  “People don’t like to be alone.  And usually the good outweighs the bad, makes the risk worth it.”  Shiro lets his mind drift and linger over the things he already misses about Adam--his smile, his strength, his wit--so Keith can see it.

There’s another memory in there, one Shiro tries to push down, but not before it sends heat curling through him, and Shiro’s reminded that he hasn’t gotten off since before Keith became a part of him.  Not with Adam, and not on his own, and suddenly it’s hard to ignore his neglected libido, especially when Keith curls around him expectantly.  “It’s that not-hunger,” Keith hums.

Shiro nods and sits back in his chair, and thinks there’s no point in holding it in, in hiding this from Keith, unless he wants to take a vow of chastity.  It was one thing to avoid sex with Adam, but there’s no conflict now that it’s just Shiro.

Shiro’s hand snakes into his pants unthinkingly, and he’s already half-hard when he touches himself, so it only takes a few light strokes to bring him to full hardness.  He sighs, a little melancholy that he doesn’t have anyone to do this with anymore, but—

“ _Shiro_ ,” Keith hisses.  “What is this?”  Black curls around Shiro’s arm and creeps toward his wrist hesitantly.  Keith manifests more of a physical form, a hand curling around Shiro’s arm as he watches him.  His eyes are sharp and assessing, and it’s...making Shiro hotter.  He pushes the thought down, but Keith seems to pick up on it, trailing his hand across Shiro’s chest and down.

Shiro bites his lip and shakes his head.  “Just...let me, okay?”  He needs this; it’s been too long and he can’t stop now until he’s finished, can’t let Keith keep him from it.

“It feels good,” Keith says slowly, and Shiro nods before he realizes it’s not a question or statement about how _Shiro’s_ feeling.

A moment later Shiro’s hand is enveloped in black—he can’t see it but he can _feel_ the change in texture as he strokes over himself—and he sucks in a surprised gasp because that’s _Keith_ and it should be weird but it only feels _good_.  He lets his other hand wander under his shirt to tweak his nipple, encouraging Keith to follow, if that’s what he’s going to do, and Keith does, hand roaming up to scratch sharp nails over them, just shy of pain.  It’s an assault on Shiro’s senses, having stimulation both there and on his dick, and it makes his breath shudder..

Keith makes a noise, and it echoes in Shiro’s mind.   _“Good_ ,” Keith croaks, “it feels good, Shiro.”  And it _does_ , but he wants to see it, too.   Shiro uses his free hand to tug his pants down enough to see black closing around his cock, slick and warm.  It tightens tentatively, and this time Keith’s voice is in tune with Shiro’s own when he groans in response.  Shiro’s still directing the motion of his hand, thumbing his head, but it’s all covered in the black of Keith, adding a toe-curling friction that makes Shiro gasp.  And it really has been a while, because his orgasm catches him by surprise, his hips stuttering and jerking with it, Keith watching him with hooded eyes.  There’s no evidence of his orgasm because it’s swallowed up in black, and Shiro’s not sure what to think of it..

Shiro tries to catch his breath, but Keith is still focused on his cock, eyes bright as black continues to slide against Shiro in search of _more_.  “K-Keith—“  He’s oversensitive and he squirms, trying to escape it, “It’s too much,” he gasps, and Keith finally backs off, though he frowns in disappointment.  Shiro drops back into his chair and closes his eyes, panting, trying to shake the burn of Keith’s gaze.

The lines between him and Keith have blurred, but this...this has given them a little definition again, and Shiro takes a moment to process it.  On the heels of it is an ache, because even though Shiro’s not _alone_ , he feels lonely—lonely for Adam, or maybe just for a pair of arms around him, for the shared afterglow of a mutual orgasm.

As soon as he thinks it, Keith is wrapping around him, tendrils of black holding him tight and making Shiro’s eyes fly open in surprise.  Keith’s form gains definition, until the tendrils wrapped around Shiro are arms, and Keith looks almost human as stares at Shiro, violet-grey eyes with yellow sclera.

“That is what your hunger wants,” Keith says.  “I understand why you crave it.  You like it— _we_ like it.  Is it necessary for survival?”

Shiro closes his eyes again.  It’s not exactly the best pillow talk, but he finds he doesn’t mind too much. “Sort of.  Not like that, exactly, but it’s needed to reproduce.”  He doesn’t have the energy to explain to Keith that there’s more to it than that, so he thinks it as best as he can, hoping Keith can pick it up from his mind.  That seems to be a thing he does, anyway.

Shiro doesn’t remember falling asleep, but he dreams that Keith lifts him out of his chair and carries him to bed, where he sprawls over Shiro like an oil-black blanket.

**Author's Note:**

> Find me on [tumblr](http://sylvermyth.tumblr.com) and cry over fluid mechanics with me.


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